Structural genomics of IncFII-FIA-FIB multidrug resistant plasmid pBTR-CTXM

Abstract:

[Background] The IncFII-FIA-FIB incompatibility group plasmids are widely encountered in Enterobacteriaceae species. They mediate the horizontal transfer of many resistance genes and lead to the upsurge of multidrug-resistant strains. [Objective] To investigate the genomic characterization of the multidrug-resistant plasmid pBTR-CTXM assigned into IncFII-FIA-FIB incompatibility group and the plasmid-mediated horizontal transfer mechanism of resistance genes of Escherichia coli BTR. [Methods] The screening of antibiotic resistance genes was determined using PCR. The transferability of plasmid pBTR-CTXM was confirmed by conjugation experiments and electroporation experiments. The minimal inhibitory concentration (MIC) values were tested by VITEK 2 Compact system. The complete nucleotide sequence of pBTR-CTXM was determined using next-generation sequencing technology from a mate pair library. Structural genomics of pBTR-CTXM was analyzed subsequently. [Results] The multidrug-resistant E. coli BTR isolate harbored the blaNDM-1, blaCTX-M-15, blaTEM, qnrD, qnrS1, mph(A), erm(B), and tetA(B) genes. The blaCTX-M-15, mph(A), erm(B), and tetA(B) genes were located on pBTR-CTXM (GenBank accession number MF156697) with 144 939 bp in length. The pBTR-CTXM could be conjugatively mobilized to the recipient strain E. coli EC600 by pNDM-BTR, a conjugative plasmid existed in the E. coli BTR. pBTR-CTXM possessed typical backbones of IncFII-FIA-FIB plasmids and a multidrug-resistant (MDR) region, which was comprised of a novel composite transposon Tn6492, the Tn2 remnant, the Tn10 remnant, the ISEcp1-blaCTX-M-15-Δorf477 unit and some insertion sequences (IS) elements. [Conclusion] The novel composite transposon Tn6492, the Tn10 remnant, and the ISEcp1-blaCTX-M-15-Δorf477 unit mediated the horizontal transfer of resistance genes and the antibiotic resistance of E. coli BTR.